1. Field of the Invention
The present invention relates to a fastening device that is particularly useful for securing an electrical conductor, such as a wire, to a conductive stud which has a base extending generally perpendicularly to the stud axis. Fastening devices of this type are often used in the automobile industry to interconnect electrical conductors such as the various lead wires and terminal studs in automobile systems which warn occupants to buckle their seat belts. In these applications, because of the large number of connections made and because of the large number of automobiles produced, it is desirable that fastening devices be designed for easy installation on the stud so that the connection can be made positively, quickly and inexpensively. The fastener should also be easily removable by hand without destroying the stud in order to facilitate subsequent repair of the electrical system. Moreover, it is of course desirable to insulate the electrical connection to prevent short-circuiting as well as to prevent injury to assembly and repair personnel.
2. Description of the Prior Art
Various fastening devices which are engagable on threaded or initially threadless studs are known. However, many of these devices are, for good reason, not intended to be used as electrical conductor connectors. For example, neither the conductive components of nor the interconnections which would be made by some fastening devices are insulated (see e.g., U.S. Pat. Nos. 2,334,046 (Tinnerman); 2,339,664 (Tinnerman); 2,846,744 (Becker); and 2,584,828 (Ballou, Jr.)).
Other fastening devices are characterized by certain drawbacks even though their metal components are insulated by some form of cover. For example, U.S. Pat. No. 3,507,182 (Tinnerman) discloses a fastener comprising a sheet metal nut clamped between interengaging plastic nut cover components. Considerable expense is required to make and assemble the various components of this composite construction. Therefore, its practical usefulness is limited in applications where large volumes of inexpensive fasteners are needed. The fastener also has a hexagonal shape which assists in providing positive engagement between the nut and nut cover but this shape is not the best for a fastener designed to be installed or removed by hand.
Moreover, this Tinnerman device, as well as that disclosed in U.S. Pat. No. 2,582,580 (Bedford, Jr.), would not provide a good electrical connection between the stud to which it is attached and a lead wire unless the stud had a broad conductive base because the conductive fastener component is isolated from the wire. Similarly, U.S. Pat. No. 3,007,726 (Parkin) discloses a device which would only provide a good electrical connection if the stud had a specially formed base against which the lead wire could be clamped.
Further, fastening devices which are designed for easy installation on a threaded or initially threadless stud have been proposed. For example, self-threading devices which cut threads into a stud when installed thereon are disclosed in U.S. Pat. Nos. 2,986,059 (Duffy et al.); 3,368,444 (Holton); 3,456,705 (Tinnerman); and 3,507,182 (Tinnerman). The device disclosed in the Bedford, Jr. Patent may be pushed onto a stud but may be rotationally removed. However, these devices exhibit many of the same deficiencies described above when used as electrical connectors.
The various problems encountered in use of prior art fasteners are aggravated by practical production problems. In particular, plastic from which nut covers are often made, has a tendency to flow or "creep". Therefore, these covers tend to yield and loosen on the sheet metal nuts after they have been assembled making subsequent removal of the fastener difficult.